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Flexible phones

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You’re inevitably late to your 9:30 a.m. class and pedaling as fast as your legs can allow. Your phone slips out of your pocket, but your case wasn’t rated for bicycle drops. You pedal back, embarrassed and turn your phone over to an ornate (and expensive) spiderweb on your screen.

With new flexible phones, you can say, “Goodbye spiderweb cracks; hello indestructible glass!”

Samsung announced its first flexible screen in 2011, and in 2018 we might just see this technology go mainstream with the rumored Samsung Galaxy X. But how do these bendable phones actually work?

Traditional Organic Light Emitting Diode (OLED) screens convert electricity into light with the help of organic molecules that allow for the manufacture of screens 0.2mm thin. OLED screens integrate the circuitry with the glass, but this makes the screen brittle and prone to shattering.

Current flexible display technology transcends the problem by integrating the circuitry with layers of flexible plastic film. But this introduces another problem: the touch layer that senses the user’s fingers. The touch layer is conductive, transparent film that lives underneath the glass and covers the display. Electrodes on the phone run a current through the touch layer, so when the user touches a point, they can detect the decrease in current and determine the point.

Modern smartphone screens use an alloy of indium, tin and oxygen for the touch layer. But as those who have dropped a phone can tell you, it’s not very shatterproof. Therefore, making a flexible touchscreen requires advances in the touch layer.

The touchscreen is only one component in a smartphone: there’s still the circuit board, processors, camera and batteries that would also be a challenge to integrate into a flexible phone. Small consumer electronic devices, such as smartphones, canonically use lithium-ion batteries. These batteries contain a separator between the anode (negative side) and cathode (positive side).

When Li-ion batteries discharge, the anode releases lithium ions, which migrate to the cathode through an electrolyte; while charging, the lithium ions migrate back to the anode. A separator between the anode and cathode blocks the flow of electrons within the battery, thereby producing a current.

Because the electrolyte is traditionally a flammable polymer, Li-ion batteries work best as an inflexible square at the phone’s heart. Li-ion batteries that use a solid electrolyte avoid these issues, yet they don’t store that much power — yet another obstacle to overcome. Samsung is rumored to have solved this issue in the Galaxy X with a curved battery that boasts a much higher power capacity than current smartphones on the market.

It’s also important to note the trade-offs to these flexible phones. Glass touchscreens feel more responsive than the plastic touch screens that would be used in flexible phones. Even though flexible screens cannot shatter, they collect scratches much more easily than glass panels.

There are also aesthetic concerns for an $1,800 phone. Samsung, Huawei and other smartphone manufacturers have been moving toward phones with glass bodies — see the notable introduction of the Samsung Galaxy S6 at Mobile World Congress 2015. Considering the phone industry’s design shift, glass and aluminum simply feel and look more premium than plastic because they’re more solid and durable. Flexible smartphones cannot feel as solid as a traditional smartphone.

Samsung’s Galaxy X launch has the potential to transform the flexible phone from a proof of concept into the next wave of smartphone innovation.

Personally, I’ll stick with my traditional handset before dropping $1,800 on an untested product. I was unhappy enough when Samsung forced a curved “edge” display on me. Curved “edge” displays seem to blur the line between functional advance and marketing gimmick aimed at squeezing another $200 out of the consumer. Flexible phones will similarly need to prove their worth before everyone and their mother cough up an extra $1,000 more than the cost of a conventional phone.

I can certainly see the appeal of having a shatterproof phone that can bend into any tight pocket. Not insignificantly, it would cut back on all those shameful trips to the Apple store!

 

Contact Alexander Ke at alexke ‘at’ stanford.edu.

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